In a multi-color electrophotographic imaging system, latent images are formed in an imaging region of a moving photoconductor. Each of the latent images is representative of one of a plurality of different color separation images. The color separation images together define an overall multi-color image. The color separation images may define, for example, yellow, magenta, cyan, and black components that, upon subtractive combination on output media, produce a visible representation of the multi-color image. Prior to an imaging cycle, a uniform charge is applied to the surface of the photoconductor. Each of the latent images is formed by scanning a modulated laser beam across the moving photoconductor to selectively discharge the photoconductor in an image-wise pattern. Appropriately colored developers are applied to the photoconductor after each latent image is formed to develop the latent images. The resulting color separation images ultimately are transferred to the output media to form the multi-color image.
In some electrophotographic imaging systems, the latent images are formed and developed on top of one another in a common imaging region of the photoconductor. The latent images can be formed and developed in multiple passes of the photoconductor around a continuous transport path. Alternatively, the latent images can be formed and developed in a single pass of the photoconductor around the continuous transport path. A single-pass system enables multi-color images to be assembled at extremely high speeds. An example of an electrophotographic imaging system configured to assemble a multi-color image in a single pass of a photoconductor is disclosed in co-pending U.S. patent application Ser. No. 08/537,296 to Kellie et al., filed Sep. 29, 1995, and entitled "METHOD AND APPARATUS FOR PRODUCING A MULTI-COLORED IMAGE IN AN ELECTROPHOTOGRAPHIC SYSTEM."
In an electrophotographic imaging system as described above, the latent images must be formed in precise registration with one another to produce a high quality image. In systems incorporating a photoconductor belt, precise registration can be difficult due to deviation of the belt from the transport path in a direction generally perpendicular to the transport path. Specifically, the photoconductor belt can undergo side-to-side movement (i.e., belt walking) during travel. The imaging region in which the latent images are formed is commonly fixed relative to the edge of the photoconductor belt. However, the scanning beam used to form each latent image in the imaging region is fixed relative to a start-of-scan coordinate. The side-to-side movement of the photoconductor belt, known as belt walking, can cause movement of the imaging region relative to the start-of-scan coordinate. As a result, misregistration can occur between different scan lines and between different latent images. This misregistration can significantly degrade image quality. In particular, the misregistration can produce visible artifacts in the final multi-color image upon transfer of the misregistered color separation images to the output media.